diff --git a/core/lib/Drupal/Component/Utility/Unicode.php b/core/lib/Drupal/Component/Utility/Unicode.php
index 4a43aa8..86335fb 100644
--- a/core/lib/Drupal/Component/Utility/Unicode.php
+++ b/core/lib/Drupal/Component/Utility/Unicode.php
@@ -584,7 +584,7 @@ public static function mimeHeaderEncode($string) {
       $output = '';
       while ($len > 0) {
         $chunk = static::truncateBytes($string, $chunk_size);
-        $output .= ' =?UTF-8?B?' . base64_encode($chunk) . "?=\r\n ";
+        $output .= '=?UTF-8?B?' . base64_encode($chunk) . "?=\r\n ";
         $c = strlen($chunk);
         $string = substr($string, $c);
         $len -= $c;
diff --git a/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php b/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php
index 1a8a08a..2f8c7e7 100644
--- a/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/UnicodeTest.php
@@ -91,9 +91,9 @@ public function providerTestMimeHeader() {
     return array(
       array('tést.txt', '=?UTF-8?B?dMOpc3QudHh0?='),
       // String longer than 47 characters including special characters. The
-      // result is an encoded chunk splitted in two parts separated by a CLRF
+      // result is an encoded chunk splitted in two parts separated by a CRLF
       // and a space.
-      array('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaà', "=?UTF-8?B?YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFh?=\r\n  =?UTF-8?B?YWHDoA==?="),
+      array('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaà', "=?UTF-8?B?YWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFh?=\r\n =?UTF-8?B?YWHDoA==?="),
       // Simple ASCII characters.
       array('ASCII', 'ASCII'),
       // Long ASCII string (more than 47 characters).